This invention relates to a machine tool, such as a lathe, capable of properly performing the machining mixed with various kinds of machining modes, such as end face machining and outside diameter machining, with small kinds of tools.
In a conventional way, the machining with various kinds of machining modes, such as end face machining and outside diameter machining, is executed using a lathe. Since the direction that the cutting tool edge is put on a workpiece is different according to each machining mode in normal cases, a plurality of tools where the directions of the cutting tool edge are different are prepared, and then, it is necessary to selectively adopt these tools every each machining mode. That is, it is necessary to change tools every change of each machining mode.
In recent years, the lathe capable of rotating and positioning the direction holding a tool with the Y-axis set on a tool rest as its center has been proposed (for example, as shown in the Japanese patent application No. 328905/1998). But, even in this lathe, the method of machining a plurality of machining modes with a single tool by properly changing the direction of the cutting tool edge on the workpiece can not be established.
Then, the object of the present invention is to provide a machine tool capable of machining a plurality of machining modes with a single tool, wherein the loss of machining time with tool change can be decreased and the number of tools to be prepared can be decreased, taking the above-mentioned circumstances into consideration.
In order to solve the above-mentioned problems, claim 1 of the present invention is machine tool having workpiece holding means for holding a workpiece with a first axis as its center being free to axially rotate and drive, a tool rest being free to move, drive and position with respect to the held workpiece in a plane having the first axis and a second axis crossing with the first axis, and a tool holding body for attachably and detachably holding a tool on its top end side, provided being free to rotate and position with respect to the tool rest with a third axis set at the tool rest as its center, crossing with the plane having the first axis and the second axis, said machine tool further comprising:
machining form designating means for designating machining shape of the workpiece;
angular position computing portion for computing angular position around said third axis for respectively positioning a single tool in the plural number of directions of the tool edge according to said designated machining shape;
tool rotating positioning means for positioning the tool held by said tool holding body in order in the plural number of directions of the tool edge according to said machining shape by rotating and positioning the tool holding body around said third axis on the basis of the angular position computed by said angular position computing portion at the time of machining; and
machining execution means for executing the machining of said machining shape corresponding to said direction of the tool edge in a state that said tool is positioned in each tool edge direction.
According to claim 1, the angular position around the third axis for respectively positioning a single tool in the plural number of directions of the tool edge according to the designated machining shape is computed. At the time of machining, the tool held by the tool holding body is positioned in the plural number of directions of the tool edge according to the machining shape in order by rotating and positioning the tool holding body around the third axis on the basis of the computed angular position. By doing so, the machining with the plural number of directions of tool edge can be performed with a single tool. That is, according to the present invention, the loss of machining time by the change of tools can be decreased and the number of tools to be prepared can be decreased.
Besides, in claim 2 of the present invention, said angular position computing portion has machining mode detecting portion for detecting machining mode a concerning said designated machining shape, and the angular position around said third axis for respectively positioning said single tool in the plural number of directions of the tool edge is computed for each machining mode detected by said machining mode detecting portion.
According to claim 2, the angular position around the third axis for respectively positioning a single tool in the plural number of directions of the tool edge is computed every each machining mode. Then, the number of computing the angular position can be decreased when the machining having the plural number of the same machining mode is performed.
Accordingly, the machining program composing time can be shortened and the operation time of the whole machining can be shortened.
In claim 3 of the present invention, said angular position computing portion has angular position initial value memory portion for memorizing angular position initial value set for each machining mode in advance, and interference judging portion for judging interference between a tool and a workpiece when said angular position initial value set for the machining mode is adopted as an angular position, for each machining mode detected by said machining mode detecting portion, and on the basis of the judgement results of said interference judging portion, said angular position initial value or the value changed said angular position initial value is adopted as the angular position around said third axis with respect to said machining mode detected.
According to claim 3, the angular position initial value is firstly tried to be adopted when the angular position is computed for each machining mode. When the tool and the workpiece interfere with each other, the angular position initial value is changed so that proper angular position is computed. That is, the angular position initial value is adopted as the angular position to be obtained to the utmost so as to extremely save the work for specially computing another angular position different from the angular position initial value. By doing so, the machining program composing time can be shortened and the operation time of the whole machining can be shortened.
In claim 4 of the present invention, said angular position computing portion has tool minimum held angle memory portion for memorizing tool minimum held angle between a tool and a workpiece at the time of machining, set in advance concerning a tool to be used for machining, and angle position change computing portion for computing the angular position around said third axis with respect to said machining mode detected, on the basis of the tool minimum held angle concerning said tool memorized in said tool minimum held angle memory portion when said interference judging portion judges that the tool and the workpiece interfere with each other.
According to claim 4, when the judgement is that the tool and the workpiece interfere with each other, the angular position is computed on the basis of the tool minimum held angle. Then, the interference between the tool and the workpiece can be certainly avoided by adopting the angular position obtained by this computing. That is, since the angular position computed by the angular position change computing portion is credible proper value, it is not necessary to judge the interference between the tool and the workpiece when the angular position computed by the angular position change computing portion is adopted. Then, it is not necessary to repeat the judgement in order to obtain one angular position. Accordingly, the machining program composing time can be shortened and the operation time of the whole machining can be shortened.
In claim 5 of the present invention, said tool minimum held angle memory portion memorizes tool minimum held angles concerning a plurality of tools to be used for machining.
According to claim 5, the tool minimum held angle memory portion memorizes the tool minimum held angle for a plurality of tools to be used for machining.
Then, the machine tool having the effects in claims 1 through 4, selectively using a plurality of tools, such as the tool for rough machining and the tool for finishing machining, can be provided.